Low bandwidth television

ABSTRACT

The present invention is concerned with client-side production in a personal computer environment of low bandwidth images and audio. A series of low bandwidth still images along with a “script” and audio data is sent over a network in a client/server architecture or is read from a compact disk or other memory. A “director” module residing in a client personal computer uses the “script” to tell the computer how to execute a sequence of “moves” on the still images. These moves include cuts, dissolves, fades, wipes, focuses, flying planes and digital video effects such as push and pull. Moves within a still image occur in real time, and are relatively smooth and continuous as compared to prior art network video. Low bandwidth is achieved because most of the production is done at the client location without relying upon slow, bandwidth-limited downloading of conventional network video formats.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/071,930, filed on Jan. 20, 1998 and entitled “LOW BANDWIDTHTELEVISION”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to image processing, andspecifically to production of images and audio in a personal computerenvironment.

2. Discussion of the Prior Art

An important issue in digital technology is providing video images on apersonal computer. These images are transmitted across the Internet andother networks, across telephone lines with modem-to-to modemconnections, or received from compact disk read-only memories (CD-ROMs).The speed of a modem is commonly the limiting factor in sending realtime, continuous video information across the Internet, over corporateintranets or local area networks. In comparison, continuous networktransmission of audio data does not present significant difficulties.

Table 1 shows theoretical bandwidth maxima for various networkarchitectures. Modem-to-modem connections across lines in plain oldtelephone service (POTS) have a theoretical bandwidth of 3,360 bytes persecond, while connections across the Internet with a modem or singleISDN are limited to 5,600 bytes per second. Dual ISDN networkarchitectures transmit a maximum of 11,200 bytes per second, whilecorporate local area networks with 10 BaseT connections have acapability of transmitting one megabyte per second. With the exceptionof telephone line connections, these other techniques involvenon-continuous, packet-switched data. Satellite and cable architecturesare also possible, but have not yet been widely adopted and presentother difficulties.

TABLE 1 Theoretical Maximum Continuous Network Architecture BandwidthBandwidth Modem to modem over POTS 3,360 bytes/sec Yes Internet withmodem 5,600 bytes/sec No Internet with single ISDN 5,600 bytes/sec NoInternet with dual ISDN 11,200 bytes/sec  No Corporate 10BaseT Onemegabyte/sec No

On the other hand, computer memories and processor speeds have maderapid advances. Personal computers have hard drives accommodating manygigabits of data, and the price of memory chips is decreasing. Processorspeeds approaching 300 MHz are available, and speeds of several GHz arecontemplated.

To view a still or motion picture from the Internet on a personalcomputer, a user conventionally downloads video data from a web site byclicking on a web link. Often, however, it is necessary to separatelydownload (or otherwise obtain) software, e.g. Adobe Acrobat, in order todisplay a particular image format. Images are frequently compressed fortransmission over networks or storage on disks. Compression algorithms,such as JPEG and MPEG, using discrete cosine transfer (DCT) methods,produce serviceable images but compromise image size, image quality,definition, and acquisition speed. Image latency is also sacrificed. Auser must wait while an entire image or series of images is buffered ina client side personal computer prior to display. Image transmission issometimes interrupted due to network errors and traffic. Streamingtechniques allow a user to begin viewing the images immediately whiledownloading, but streaming still sacrifices image quality and latency.

Currently, International Telecommunications Union Standard ITU-R 601 fordigital formats in professional video production (i.e. NTSC) requires720 by 486 pixels per frame in the scanned image, and an eight-bit 4:2:2sampling of Y, R-Y, B-Y color components at sixty frames per second.This results in a data stream of 20 megabytes per second if the formatis to remain uncompressed and if the images are to be viewedcontinuously in real time. Clearly, this is greater than the fastestrate for 10 BaseT of one megabyte per second. A compression ratio of 5:1is the most that is considered desirable for production marketplaceimage quality, but this only reduces the necessary data rate to 4megabytes per second. Using 4:1:1 sampling, other conventional digitalvideo production techniques (e.g. DVC Pro and DV Cam) produce amarginally improved data rate of 3 megabytes per second. Compressionratios of 30:1 are sometimes used for previewing and editing of videoimages, but this only yields a data rate of 700 kilobytes per second.Data rates for these formats are summarized in Table 2.

TABLE 2 Digital Video Format Compression Ratio Data Rate ITU-R 601  1:1(uncompressed)  20 megabytes/sec ITU-R 601  5:1  4 megabytes/sec DV (DVCPro &  5:1 (using 4:1:1 sampling)  3 megabytes/sec DV Cam) ITU-R 60130:1 (offline quality) 700 kilobytes/sec

Comparing this to the standard modem of 56 kilobytes per second, thereis a readily apparent, significant gap between requirements for ITU-R601 and present-day hardware transmission capabilities. A furthercompression ratio of 125:1 on an already-compressed and marginallyacceptable 30:1 compressed image, i.e. a total compression of 750:1, isneeded to transmit ITU-R 601 data across a 56 k modem.

Present methods of displaying moving objects on web pages involve eitherbit-mapped or vector approaches. Simple moving icons on a web page areproduced by changing only part of the image in every frame. For example,Microsoft® and Netscape® browsers show moving traces around their logoswhile a processor is retrieving a page. Advertisements on web pages alsodisplay moving images. The bandwidth for these images is reduced bymaking the images smaller so that fewer bits are needed for each frame,or by slowing down the frame rate so that the images appear to movediscontinuously.

High definition television (HDTV) attempts to simplify the display ofvideo images and reduce bandwidth by recognizing constant areas within avideo picture and retaining much of the information from a previousframe. While HDTV developed concurrently with MPEG and JPEG, HDTV isbroadcast-oriented and does not lend itself to network transmission orpersonal computer applications.

It is expected that bandwidth will continue to be the bottleneck innetwork transmission for the foreseeable future. Thus, there is anoutstanding need in the prior art to be able to send professionalquality video images across networks through ordinary modems by takingadvantage of plenary memory and processor capacities within personalcomputers, and thereby reducing reliance on transmission hardware. Thereis also a need to create compelling new video experiences in personalcomputers.

SUMMARY OF THE INVENTION

The present invention is concerned with client-side production in apersonal computer environment of low bandwidth images and audio. Aseries of still images in an image module along with a “script” moduleand an audio module are sent over a network in a client/serverarchitecture or are read from a compact disk or other memory. A“director” module residing in memory (e.g. on hard disk) of the clientpersonal computer uses the “script” to tell the computer how to executea sequence of “moves” on the still images. These moves include, but arenot limited to, cuts, dissolves, fades, wipes, focuses, flying imageplanes, and digital video effects such as push and pull. The directormodule is either downloaded from a network on a one-time basis oruploaded from a floppy or compact disk.

Production sequences are in real time, as well as being relativelysmooth and continuous as compared to prior art network video. In orderto permit viewing as soon as possible and to avoid caching, the scriptmodule is transmitted to the personal computer along with preliminaryimages, so playback begins immediately. Low bandwidth is achievedbecause a majority of the production is done at the client location andthe transmission of still pictures, audio data and script is relativelyrapid. Images are always displayed in real time and in full screenformats. If necessary to prevent latency delays, the director modulesinserts stand-in from stock footage, animation and loops so that aviewer always has a continuous visual and audio experience.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, as well as otherfeatures thereof, reference may be had to the following detaileddescription of the invention in conjunction with the drawings wherein:

FIG. 1 illustrates a network architecture of the present invention;

FIGS. 2(a)(i)-(iii) show a first move of a bit-mapped image;

FIGS. 2(b)(i)-(iv) show a second move of a bit-mapped image;

FIGS. 2(c)(i)-(iv) show a third move of a bit-mapped image;

FIGS. 2(d)(i)-(iv) show a fourth move of a bit-mapped image;

FIG. 3 illustrates a flowchart for playing back visual and audiosequences;

FIGS. 4(a) and (b) illustrate software modules for producing visual andaudio sequences; and

FIG. 5 shows a user interface for authoring visual and audio sequences.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a general overview of a client/server architecture of thepresent invention. Client personal computer 100 is connected throughmodem 120 and network 125 to server 130. Computer 100 includes displayscreen 140, stereo speakers 150, disk drives 160, and hard drive 170containing a number of software modules. Server 130 has a memorycontaining other software modules, and server 130 is connected to aplurality of other clients 180, 181 and also to a production client 185.Production client 185 authors production images 190 shown on display 140of personal computer 100 as well as providing a director module forone-time plug-in at client computer 100.

FIGS. 2(a) to 2(d) show selected “moves” characteristic of the lowbandwidth television of the present invention. FIG. 2(a) shows a flyingvideo plane. A still picture 210 of an image to be displayed on computerscreen 140 resides in the personal computer (FIG. 2(a)(i)). Images 230,230′ of picture 210 are displayed on personal computer 100 such that notall of picture 210 fits within a display window 220, 220′, but part ofthe picture 210 is cropped on the computer screen 140 as images 230,230′ (FIGS. 2(a)(ii)-(iii)). Now, picture 210 is rapidly translatedwithin the display window 220, 220′ of computer screen 140. Since theentire still picture 210 is already stored within the personal computer100 as a bit-mapped image, there is no need to download a succession ofimages from a network or disk to give the illusion of motion. Movingimages 230, 230′ are created at the client personal computer 100 fromthe bit-mapped still picture 210 stored in the computer memory. Oneapplication is a pan around of a three hundred and sixty degree scene.Once the scene is stored as a bit-mapped still picture 210 in thecomputer, the director uses the script accompanying the still threehundred and sixty degree picture 210 to simulate a camera track at anyposition around the scene.

Another application is a moving banner. The banner is stored as abit-mapped still picture 210 (FIG. 2(a)(i)), but picture 210 is croppedsuch that only one segment of the banner is displayed at one time (FIGS.2(a)(ii)-(iii)). The script accompanying the banner is used by thedirector module to move the banner from left to right across screen 140,or up, down or diagonally across screen 140. Images 230, 230′ appear tomove much more rapidly and smoothly across screen 140 than in prior artsystems because the processor of computer 100 is locally working onresident picture 210 to create images 230, 230′ and a series ofbit-mapped pictures 210 need not be continuously downloaded from anetwork.

FIG. 2(b) shows a focus/defocus move. A bit-mapped still picture 240resides in personal computer 100 along with a script module. Assumeinitially that the image is in focus and displayed on computer screen140 as picture 240 (FIG. 2(b)(i)). The script cues the director toactivate an algorithm residing on the personal computer 100 whichcalculates and displays a series of defocused images 241, 242, 243 ofthe original bit-mapped still picture 240 (FIGS. 2(b)(ii)-(iv)). Thisalgorithm is one of the utilities downloaded on a one-time basis withthe director and is optimized to produce rapid calculation of thedefocused images. Picture 240 optionally is downloaded as a pair ofpictures 240 a and 240 b, with picture 240 a (FIG. 2(b)(i)) representedthe focused or starting image and picture 240b (FIG. 2(b)(iv))represented the defocused or target image. Preferably, the defocusingalgorithm involves an optimized table representing iteratively defocusedimage states between the starting image and the target image. The scriptmay indicate that the image is initially displayed as a defocused imageand subsequently brought into focus, or vice versa.

FIGS. 2(b)(i)-(iv) also can be used to illustrate a dissolve. Picture240 is sent with the script module including a dissolve code. Thedirector contains an algorithm for executing this dissolve, preferablyusing optimized tables. The director thus tells computer 100 how tolocally calculate dissolving images 240, 241, 242, 243 at clientcomputer 100, and these images 240, 241, 242, 243 are continuously andrapidly displayed on screen 140.

FIGS. 2(c)(i)-(iv) show consecutive stages in a linear wipe. During awipe, picture 250 is made to disappear from display screen 140 across amoving line 260. Line 260 may be horizontal, vertical, diagonal,straight or curved. As line 260 moves from one side or corner of picture250 displayed on the computer screen 140 to the other side, picture 240disappears from one side of the line 260 but remains on the other side(FIGS. 2(c)(ii)-(iv)). Thus, picture 240 is “wiped out” or removed asline 260 moves across screen 140, and images 251, 252, 253 arecalculated by computer 100 with an algorithm found in the director. Wipeline 260 may also start from some place in the center of picture 240 andprocess outwards, or several wipe lines 260 may remove areas of picture240 simultaneously starting from different places on picture 240. Thekind of wipe that is to be executed by the director is indicated by thescript code accompanying picture 240, and the processor of computer 100locally calculates the wipe with algorithms found in the director. Asthe wipe line traverses across the image, a screen optionally isrevealed to have a particular background 270 (FIG. 2(c)(iv)). Background270 may be another bit-mapped image such as a photograph, text orgraphic, or the background may be a solid.

FIG. 2(d) shows a biaxial wipe. Pieces 271, 272, 273, 274 of abit-mapped picture 240 appear to split apart, and each piece 271, 272,273, 274 moves in a different direction towards the edges of the displayscreen 140 (FIG. 2(d)(i)-(iv)). One example splits picture 240 alonghorizontal and vertical axes 280, 281, with each piece 271, 272, 273,274 moving towards a respective corner of the display screen 140. Therealso may be two pieces moving along a diagonal line towards oppositediagonal sides of the screen. Once the wipe begins, the absence of theimage optionally reveals another bit-mapped image, a blank screen, aparticular color or texture.

Low bandwidth television produces a sequence of moves on stillbit-mapped images specified by an accompanying script. The productionsequence can be rapidly and consecutively strobed and repeated in aparticular order, or the sequence can be strobed and repeated in adifferent order. Repetition and looping of sequences implies that anyproduction sequence has an arbitrarily long and potentially infiniteduration. A production sequence may consist of combinations of stillimages, high resolution photographs, text graphics, high resolutiontext, and animated computer graphics. While the present embodimentcontemplates that the director primarily operates on still images, shortvideo clips residing as stock footage with the director module mayoptionally be utilized.

Low bandwidth television assumes full screen and real time display ofimages. In contrast to prior art systems where image size must be scaledand quality reduced to conserve bandwidth, the present inventionimproves the viewing experience by requiring that images cover theentire screen of the personal computer. Larger size and higherresolution pictures are possible because a majority of the productionwork is contemporaneously performed by the director at the clientlocation rather than prior to network transmission. Real time display isachieved because the image and audio modules are transmitted quicklyacross the network due to their small bandwidth. The director furtherguarantees a real time experience by inserting stock footage, loopingand stretching whenever image data is delayed due to network latency.

Each image module is generally synchronized with an audio track that issent with the script. The audio track optionally includes music tracks,Foley effects, and voiceovers. An audio engine has a capability ofmixing multiple audio tracks and adding special audio effects such asreverb and audio delays in real-time. The director module includes ahigh quality audio synthesizer having a file size of about 20 megabytes.

One major difference between the low bandwidth production system of thepresent invention and prior art video production systems is the degreeto which a finished product is sent over a network or stored on a disk.Prior art Internet video devices (e.g. MPEG) send a finished productover the network, while the present invention sends only a partialproduct and a script and then finishes the video production at theclient station with the director. Much greater bandwidth is required forthe prior systems of sending a finished series of images over thenetwork than it does to send a partially completed set of images with ascript describing how the images are to be animated, and then finishingthe animation of the images at the client computer. In a disk storageenvironment, much more disk space is required to store all of the pixelsof a series of images than to store one image and script coderepresenting how the images are to be animated.

Furthermore, the video production method of the present invention ismuch faster than prior art methods despite the reassembly time for stillimage production at the client. The speed of the prior art method ofdownloading video images from the Internet is limited by a bottleneck atthe modem. By contrast, while the video production of the presentinvention is uncompleted at the time it arrives at the client computer,the processor reconstructs the production from the images and the scriptmuch more quickly than the delay occasioned at the modem.

LBTV has a number of advantageous characteristics. It uses the sameaudio and visual language of film and video production standards. Smoothand continuous motion is produced in real-time as compared to standardmethods of viewing images from networks. There is no image latencybecause the image stills and script are transmitted rapidly incomparatively small files. Moving images are displayed in real-timebecause the director quickly calculates the production sequence at theclient computer from the stills and script. The images are displayed atsixty fields per second (in NTSC) with anti-aliased graphics,high-resolution imagery, full-screen displays and high-quality audio.These capabilities are realized because the majority of the work is doneby exploiting the processor and memory at the client computer.

Although digitized video clips may be used with LBTV, their largebandwidth implies that they are utilized sparingly. However, clipbandwidth can be decreased with keys to reduce their size, or with otherspecial effects such as strobing or posterization. In strobing, everyfifth video frame is displayed and frozen. Stock footage stored at theclient computer may also be used since it requires no networktransmission time.

The present invention also provides stand-in and loops to permit animmediate and continuous viewing experience without caching. Initially,only the script module and the earliest part of the image data from theimage module are sent across the network. Thus, presentation of imagesand sound begins immediately for the viewer without downloading of theentire image file. Neither is it necessary for the image and sound datato cache in the client computer memory. To prevent latency problems, thedirector inserts stock footage as stand-ins or causes the images alreadyreceived to loop or stretch in the production sequence. Therefore, incontrast to prior art systems where the visual stream is interrupted orthe viewer must wait while the images are downloaded, the directorensures a continuous viewing experience.

The present invention is also applicable to receiving a productionmodule comprising a script module, an image module, and an audio module,from a disk drive, e.g. a CD-ROM, rather than obtaining this module overa network. While digital video disks (DVDs) provide for real timeviewing at approximately sixty frames per second, low bandwidthproduction techniques further increase the number and run time ofprograms that can be stored on a single DVD. Moreover, LBTV does thiswithout data compression.

FIG. 3 is a flowchart of the steps in creating and viewing a lowbandwidth television production. A user first loads a plug-in in step310. The plug-in contains a director module including algorithms toperform all of the video “moves,” as well as stock footage and otherutilities. The loading is done on a one-time basis, although the plug-inmay be updated periodically, e.g. when new algorithms are added to thedirector (step 315). The plug-in may be downloaded from a networkserver, or the plug-in may be uploaded from a disk drive, for example, amagnetic disk or a CD-ROM.

A particular video production begins in step 320. The production moduleincludes an image module, an audio module and a script module.Initially, only the script module and first viewing parts of the imageand audio modules are transmitted over the network so that viewingbegins immediately without caching. Viewing is initiated either byclicking on a link in a web site and receiving transmitted data from anetwork (e.g. the Internet) via a server, or by reading from a diskdrive, for example, a magnetic disk or a CD-ROM.

The director module uses the script module to generate initial video andaudio sequences from the image module and the audio module (step 330).The video and audio sequences are played on the video screen and throughstereo speakers of the personal computer (step 340). Meanwhile, moredata from the image module and audio module are loaded across thenetwork into the client computer (step 370). The director modulecontinues to work on the newly received data from the image and audiomodules with cues from the script module to generate new visual andaudio sequences.

If there is a gap at any time in the production due to latency or datatransfer problems (step 345), the director maintains a continuous realtime presentation by inserting stock footage or providing looping (step360). As long as there is more data being received from the network(step 365), the director continues to load data from the image and audiomodules (step 370). When program data transmission is complete, a usermay return to play another video and audio sequence (step 380), orterminate the program (step 390).

FIGS. 4(a) and (b) illustrate software components of the various modulesof the present invention. The plug-in comprises director module 410,which includes full screen transition algorithms 420 and partial screeneffects algorithms 430 (FIG. 4(a)). Examples of full screen transitionsare moving bitmaps 421, wipes 422, and animation programs 423. Director410 further comprises instrument sample libraries 440, stills 450, andstock footage 460. Stock footage 460 may include short video clips. Eachof the modules is on the order of 20megabytes. Software algorithms ofdirector module 410 are designated by Global Unique Identifiers (GUIs)to permit indexing of algorithms.

Production module 470 includes script module 475 with commands in anedit decision list (EDL), image module 480 having bit-mapped images ofthe still pictures utilized in the production, including photographs481, graphic images 482, and short video clips 483 (FIG. 4(b)). Audiomodule 490 includes music score 491, voiceovers 492 and sound effects493. Production module 470 further includes optional new effects 495,which may be identified as needed for a specific production module 470.New effects software algorithms 495 are identified by the edit decisionlist of script module 480 via respective GUIs to determine whetheralgorithms 495 are already present in director module 410.

FIG. 5 illustrates a User Interface (UI) for an authoring tool to createproduction modules 470 as a series of pages 510. A user first specifiespage 511 corresponding to a first in a series of effects in a sequence.Button bars 520, 521, 522, 523 are selected to edit pages 510. EDLcommands are attached to page 511 by clicking on button bars 520-523 tocreate script module 480. Bit-mapped still image files are attached topage 511 to form image module 490, and sound effects files are attachedto page 511 to make audio module 480. Preview window 530 displays stillbitmapped images, and a list of file names for image, audio and script(EDL) files is displayed in preview window 540. Once a bitmapped image,audio file, and edit decision list are associated with page 511, theprocess is repeated for pages 512, 513, 514, etc. Production module 470is complete once all of pages 510 are created and assembled. Aproduction editor can then go back and re-edit any of the pages.

A completed production module 470 is stored on server 130 as a diskfile(s), and client computer 100 contacts server 130 when a viewerdesires to watch the program. Client-side production may beginimmediately upon sending the EDL with some initial program content, andclient computer 100 performs production on-the-fly. Additional contentnot yet present at client 100 is transmitted in temporal order. Even ifa given section of the program occurs before all of the required contenthas been transferred, the playback engine ensures continuity usingstand-ins such as line drawings and looped sequences.

Although the present invention has been described in its preferredembodiments, those skilled in the art will appreciate that alternateembodiments, not specifically described herein, may be deduced withoutdeparting from the spirit and scope of the invention, which is limitedonly by the following claims.

We claim:
 1. A low bandwidth video system, comprising: a computer havinga display screen and a memory; a director module residing in saidmemory; and a script module, an image module, and an audio module;wherein said director module uses said image module and instructions insaid script module to compute a series Of real-time screen transitions;and combines said real-time screen transitions with associated audio torender a high quality digital video on said display screen.
 2. Thesystem of claim 1, wherein said director module is downloaded oruploaded on a one-time basis.
 3. The system of claim 2, wherein saiddirector module is periodically updated, as needed.
 4. The system ofclaim 2, wherein said director module is downloaded from a network. 5.The system of claim 2, wherein said director module is uploaded from afixed medium or alternate memory.
 6. The system of claim 1, wherein saiddirector module ensures real-time dynamics of said digital video byinserting stock footage or loops.
 7. The system of claim 1, wherein saidimage module contains bit-mapped still images.
 8. The system of claim 7,wherein said image module further contains short video clips.
 9. Thesystem of claim 1, wherein said audio module contains music andvoiceovers.
 10. The system of claim 1, wherein said image module andsaid audio module are transmitted over a network to said computer. 11.The system of claim 1, wherein said image module and said audio moduleare read from a fixed medium or alternate memory.
 12. The system ofclaim 1, wherein said screen transitions include a wipe.
 13. The systemof claim 1, wherein said screen transitions include a focus or defocus.14. The system of claim 1, wherein said screen transitions include afade.
 15. The system of claim 1, wherein said screen transitions includea dissolve.
 16. The system of claim 1, wherein said screen transitionsinclude a translation of images and said images are cropped so that onlya portion of said images are visible as a new piece of said images movesacross said display screen.
 17. The system of claim 1, wherein saiddigital video is initiated by sending only said script module andpreliminary pieces of said image module and said audio module, and saiddirector module continues to receive pieces of said image module andsaid audio module as said digital video is playing.
 18. The video systemof claim 1, wherein said director module comprises screen transitionalgorithms which are executed pursuant to the instructions, found insaid script module, to compute said real-time screen transitions. 19.The video system of claim 18, further comprising a new effects moduleincluding new effects algorithms; wherein said director module willexecute said new effects alorithms per the instructions, found in saiddirector module, to compute said real-time screen transitions.
 20. Amethod of rendering low bandwidth video, comprising the steps of:receiving an image module, an audio module and a script module at acomputer; allowing a director module to use said image module andinstructions in said script module to compute a series of real-timescreen transitions; and allowing said director module to combine saidreal-time screen transitions with associated audio to render a highquality digital video on a display screen of said computer.
 21. Themethod of claim 20, wherein said receiving step comprises receiving saidimage module, said audio module and said script module from a network.22. The method of claim 20, wherein said receiving step comprisesreceiving said image module, said audio module and said script modulefrom a fixed medium or alternate memory.
 23. The method of claim 20,further comprising the step of: loading said director module, on aone-time basis, into said computer.
 24. The method of claim 20, furthercomprising the step of: periodically updating said director module, asneeded.
 25. The method of claim 20, further comprising the step of:adding stock material or looping segments into said digital video toeliminate gaps in said digital video and to ensure real-time continuity.26. The method of claim 20, further comprising the step of: initiatingsaid digital video by sending only said script module and preliminarypieces of said image module and said audio module, with said directormodule continuing to receive pieces of said image module and said audiomodule as said digital video is playing.
 27. A computer readable mediumcomprising program instructions for displaying low bandwidth videoimages by performing the steps of: receiving an image module, an audiomodule and a script module; allowing a director module to use said imagemodule and instructions in said script module to compute a series ofreal-time screen transitions; and allowing said director module tocombine said real-time screen transitions with associated audio torender a high quality digital video on a display screen of saidcomputer.